physico 5.pdf

Definition It is the process by which an organic substance is strongly heated until the whole of the carbonaceous matter burns and an inorganic residue known as ash is left behind and the process can also be termed as ashing During the strong heating, all the volatile substances escape unt...

Definition It is the process by which an organic substance is strongly heated until the whole of the carbonaceous matter burns and an inorganic residue known as ash is left behind and the process can also be termed as ashing During the strong heating, all the volatile substances escape until its mass ceases to change. On the lab scale, ignition is carried out in silica or platinum crucibles Application of ignition 1. This process is mainly used for the standardization of organic substances and crude drugs by means of gravimetric analysis, eg. Ash values, total water soluble ash value etc. 2. It is used to determine impurities of organic salts of alkali metals such as tartarates, citrates, benzoates and many drugs 3. Purity of a drug is determined by its ash content 4. Extraction Definition Extraction is the method of removing active constituents from a solid or liquid by means of liquid solvents The separation of medicinally active portions of the plant or animals tissues from the inactive or inert components by using selective solvents In this method, the wanted components are dissolved by the use of selective solvent known as menstrum and the undissolved part is the called marc. After the extraction, unwanted matter is removed. Extracts are prepared by using ethanol or other suitable solvents Extracts are preparations of crude drugs which contains all the constituents which are soluble in the solvents. Methods of extraction üInfusion üDecoction üDigestion üMaceration üPercolation üContinues hot extraction üSupercritical fluid extraction üCounter current extraction üMicrowave assisted extraction üUltrasonication-Assisted extraction ØMaceration In this process solid ingredients are placed in a stoppered container with the whole of the solvent and allowed to stand for a period of at least 3 – 7 days with frequent agitation, until soluble matter is dissolved. The mixture is then strained (through sieves/nets), the marc pressed and the combined liquids clarified (cleaned by filtration) or by decantation, after standing. Merits üSmall sample size üStrong swelling properties or high mucilage üEnergy saving process Demerits üNot exhaustively extract the drug üIt is very slow process üSolvent required is more ØPercolation üIt is continuous downward displacement of the solvent through the bed of crude drug material to get extract üMost frequently used to extract active ingredients in the preparation of tinctures and fluid extracts. üIt is the method of short successive maceration or process of displacement üA percolator which is a narrow, cone-shaped vessel open at both ends is normally used Merits üRequires less time than maceration üExtraction of thermolabile constituents can be possible Demerits üRequires more time than soxhalation üMore solvent is required üSkilled person is required Differences between maceration and percolation Maceration Percolation üSuitable method for less potent üSuitable for potent and costly and cheap drugs drugs üNo skilled operator is required üSkilled operator is required üTime consuming and problem of ü complete extraction within a incomplete extraction short time üSuitable for substances which üAttention should be paid to the are less soluble and requires particle size of the material prolonged contact with solvent throughout the process ØInfusion Fresh infusions are prepared by macerating the crude drug for a short period of time with cold or boiling water. These are dilute solutions of the readily soluble constituents of crude drugs. Types of infusion üFresh infusion: eg. Infusion of orange üConcentrated infusion: eg. concentrated infusion of Quassia ØDecoction Here, the crude drug is boiled in a specified volume of water for a defined time; it is then cooled and strained or filtered. This procedure is suitable for extracting water- soluble, heat stable constituents. Eg. Antiars Differences between infusion and decoction Infusion Decoction üUsed for soft plant parts eg. Lippia üUsed for hard plant parts eg. leaves Cinchona bark üCold or boiling water is used üBoiling water üSuitable for thermolabile üSuitable for thermostable constituents constituents üLiquid is strained and the volume is üLiquid is strained and volume not adjusted by washing marc adjusted by washing the marc üExtraction time is calculated as üExtraction time is calculated as soon as water is added soon as water begins to boil ØDigestion üThis is a form of maceration in which gentle heat is used during the process of extraction üIt is used when moderately elevated temperature is not objectionable. The solvent efficiency of the menstruum is thereby increased. Eg. Extraction of morphine Application of extraction Separation of elements Concentration of impurities Identification and quantitative definition of chemical agents or substance markers Studying of formation constant of complexes Studying of substance conditions in a solution (a charge, polymerization degree) Increase of sensitivity and selectivity of reactions Find out more